 
   If you were to remove any call to `f` this test would fail with a verify error (`f` not invoked enough).
 
-  ## Exercise 3
+  ### Exercise 3
 
   Copy the following code to the top of your testing file:
 

    (om/transact! comp '[(a-mutation)]))
  ```

  ## Exercise 6

  Write a test that verifies the UI helper requests the correct mutation


      ...body...))
  ```

  ### Exercise 4

  Write more of an integration test for `replace-pairs` that both asserts (via mocking) that `sum-sq` is called,
  but *really* allows the original `sum-sq` to generate the real value. Add assertions that talk about how every result
  is positive, even when the pairs contain negatives. The macro `provided` is the same as `when-mocking`, but allows you
  to add a string to the output (and nest the outline a level deeper) to describe what the mocking is proving.

  ## Timeline testing

  On occasion you'd like to mock things that use callbacks. Chains of callbacks can be a challenge to test, especially
  when you're trying to simulate timing issues.
